Pulse generating circuit



June 6, 1950 J. R. MOORE- 2,510,129

PULSE GENERATING CIRCUIT Filed Nov. 28, 1942 FIG.2 FIG.3

FIG.4 FIG.5

F IG. 6 INVENTOR JAMES F (.MOORE wu m r ATTORNE Patented June 6, 1950PULSE GENERATING CIRCUIT James R. Moore, Rumson, N. 1., assignor to theUnited States of America as represented by the Secretary of WarApplication November 28, 1942, Serial No. 467,265

1 Claim. (01. 25027) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes, without the payment to me of any royalty thereon.

the sine wave shown in Figure 2 is deformed in the direction of a squarewave, as shown in Figure 3.

The output of tube i2 is applied to a second This invention relates topulse generating 5 overdriven amplifier tub 20. In the specificcircircuits. cuit here illustrated, the coupling is a resistance Thereare a number of fields in which it is coupling utilizing a blockingcondenser 22 and a necessary to provide electrical energy in the formbiasing resistor 25. Tube 29 is overdriven, and its of sharp pulses,that is, pulses of very short duraoutput assumes a substantially squarewave form, tion, with intervals of relatively long duration as shown inFigure 4. therebetween. Pulse-echo systems for locating In order theconvert the square wave of Figure and ranging are an important example.4 to the pulse wave of Figure 5, I emplo an One known method ofobtaining pulse-energy R. C. circuit having a time constant which isvery involves the use of a gas tube. However, this small compared to theperiod of the sine wave and method has a number of disadvantages. On is5 squar wave. Specifically, the R. C. circuit comthat it is difiicult tohold the pulse energy conprises a condenser 26 and a resistor 28connected stant in phase. Another is that a gas tube circuit in serieswith each other and in shunt (with reis slow to start. Still another isthat it is affected spect to radio frequency) and with the plate rebyexternal temperature, and may fail in extrema sistor 313 of tube 20. Thecondenser 25 being summer or winter weather. 20 small is quickly chargedto maximum potential. The primary object of my invention is to over-Current flows through the resistor 28 only during come the foregoingdisadvantages, and to provide the instant of charging (or discharging)of cona pulse generating apparatus not requiring the denser 26;consequently, potential is developed use of a gas tube. Still anotherobject is to obtain across the resistor 28 of the R. C. circuit for onlyunidirectional pulse energ derived from alter- 2 an instant during eachhalf cycle of the square nating current. wave. In other words, thepotential developed To the accomplishment of the foregoing genacrossresistor 28 is a bidirectional pulse of the eral objects, and such othermore specific objects character illustrated in Figure 5. as hereinafterappear, my invention consists in This bidirectional pulse may berectified, if unithe apparatus elements and their relation one to 30directional pulses are wanted. In the present another as ar hereinafterdescribed and sought case the pulse potential is applied to the inputcirto be claimed in the following specification. The cuit of a tube 32.A negative biasing potential is specification is accompanied by adrawing in supplied at terminal at, said potential being sulfiwhiehciently high to cause the tube 32 to operate as a Figure 1 is awiringdiagram for apparatus em- 35 class C ampl fie he operation is such thatbodying features of my invention; there is no plate current except whena positive Figure 2 illustrates a sine wave input; pulse is applied tothe grid. The negative pulses Figures 3 and 4 show how the sine wave isdemerely drive the grid more negative, and no plate formed into a squarewave; current flows. In consequence, onl intermittent Figure 5illustrates a bidirectional pulse obunidirectional pulses of currentflow through the tained from the square wave; and anode impedance 36.

Figure 6 shows a unidirectional puls produced This output may beutilized or further applied f om the bidirectional pulse. in any desiredmanner. In the present case, the Referring to the drawing, alternatingcurrent pulse is fed to another tube through a resistance having anapproximate sine wave form, as shown coupling mad up of a blockingcondenser 38 and in Figure 2, is applied across the input circuit oftube l2. The particular circuit used between the control electrode M andthe cathode is of tube I2 is not illustrated, as it is not a novel partof the present invention. The tube I 2 is :overdriven, that is, it isoperated beyond the saturation point of the characteristic curve on thepositive grid swing, and beyond cutoiT on th negativ grid swing. Theoutput current is therefore limited,

and the potential appearing across the plate resistor ['8 is flattenedat the top and bottom. Thus a bias resistor 6!]. In such case, it is thechange in potential at th point 42 or across the resistor 36 that isutilized. This is indicated in Figure 6, which shows the negative pulsesor sharp drops in potential accompanying the pulse current flow throughthe output impedance 36.

It is believed that the construction and operation of my improved pulsegenerating circuit, as well as the advantages thereof, will be apparentfrom the foregoing detailed description.

It will be understood that if square wave energy is available, thright-hand portion only of the circuit need be employed, that is, theoverdriven amplifier tubes I2 and 20 may be omitted, and the square wavepotential may be applied directly .to the R. C. circuit 26, 28. It willalso be understood that if bidirectional pulse energy is desired, thetube 32 may b omitted, or may be differently biased so that bothpositive and negative pulses will manifest themselves in the outputcircuit of the tube.

It will therefore be apparent that while I have shown and described myinvention in a preferred form, changes and modifications may be made inthe apparatus disclosed, without departing from the spirit of theinvention as sought to be defined in the following claim:

I claim:

Apparatus for changing asine wave to short unidirectional pulses, saidapparatus comprising resistance coupled first and second tubes, saidtubes being overdriven by the sine wave in order to produce a squarewave, each of said tubes being driven to saturation and to cutoff by thepositive and negative portions, respectively, of the wave appliedthereto, the output circuit of the second overdriven tube comprising aplate resistor and an R. C. circuit in shunt relation-thereto, a thirdtube having its control electrode circuit connected across the resistorof the aforesaid R. C. circuit, the time constant of said R. C. circuitbeing very short relative to the period of the alternating :current andthereby producing .sharp bidirectional pulses, said third tub beingnormally biased to cutofi, whereby only alternate pulses appear in theoutput circuit of said third tube.

JAMES R. MOORE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

